(1) Field of the Invention
The present invention relates to the alternate pressurization and depressurization of a chamber, for example an intermediate storage hopper which forms part of a blast furnace charging installation, and particularly to enhancing the service life of apparatus employed in such pressurization and depressurization. More specifically, this invention is directed to values which are peculiarly well suited to use in pressure equalization or isolation systems. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
(2) Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use in equipment ancillary to blast furnaces of the type which operate with high counter-pressures in the region of the furnace throat. In order to maximize the efficiency of operation, such furnaces are provided with pressure equalization chambers, for example in the form of intermediate charge storage hoppers, which enable the furnace to be charged while in operation without undergoing any appreciable pressure losses. Such chambers must be equipped with pressure equalization valves whereby they may be alternately supplied with ambient air and subjected to pressure. An example of a pressure equalization valve suitable for use with blast furnaces may be found in copending U.S. patent application Ser. No. 770,193, now U.S. Pat. No. 4,162,784, which is assigned to the assignee of the present invention; U.S. application Ser. No. 770,193, now U.S. Pat. No. 4,162,784, corresponding to Luxembourg Pat. No. 74,505. Reference may also be had to U.S. Pat. No. 3,693,812 for a disclosure of a furnace charging installation including two intermediate storage hoppers which are alternately isolated from the pressure conditions prevailing within the furnace and the ambient atmosphere by pressure equalization valves.
The valve described in copending application Ser. No. 770,193, now U.S. Pat. No. 4,162,784, particularly with respect to FIG. 2 thereof, comprises a mushroom-shaped sliding closure device, hereinafter referred to as the valve member, which is raised from its seat in order to give passage to the gas under pressure. The valve member remains in the gas stream when the valve is in the open condition and is therefor exposed to the erosion and corrosive effects of materials entrained by the gases passing through the valve. Accordingly, both the valve member and the valve seat of the valve of copending application Ser. No. 770,193, now U.S. Pat. No. 4,162,784, experience comparatively rapid wear and therefor have to be replaced or repaired on a relatively frequent basis. Also, by reason of its design, the valve of the copending application has to be installed in a curved section of the conduit through which the gas is passing and the problems associated with wear of the seat and valve member are thus intensified. The major disadvantage associated with wear of the valve components resides in the considerable time consumed by the operation of replacing the seat and valve member since such maintenance operation requires a lengthy stoppage of the furnace. The time consumed by the service procedure is, in part, a result of the fact that the conduit in which the valve is installed and/or the valve itself has to be dismantled in order to give access to the valve seat and the valve member.
Continuing with a discussion of the environment of a shaft furnace, various types of valves have been proposed wherein the valve member is pivotally mounted so as to be capable of movement out of the gas stream when the valve is in the open condition. While valves which employ pivotal valve members are characterized by reduced wear when compared to valves of the type shown in application Ser. No. 770,193 now U.S. Pat. No. 4,162,784, particularly on the sealing surfaces of the valve member, they nevertheless suffer from the drawback that replacement of the valve seat requires a lengthy furnace shut-down incident to the dismantling of the conduit in which the valve is installed. It may be noted, however, that access to the valve member is somewhat easier in those pressure equalization valves wherein the valve member is mounted on a pivoting support arm since it is possible to move the arm to a position where the valve member will extend through a lateral aperture in the conduit. Obviously, if access to the valve member is to be provided in this manner, the amplitude of the pivoting movement must be fully adequate. This, however, involves a further drawback inasmuch as the amplitude of displacement of the piston of the hydraulic jack, which is the customary means of actuating the valve, must be quite large thus requiring a correspondingly high consumption of hydraulic fluid. An isolation valve wherein the valve member is mounted on a pivotal arm and actuated by means of a hydraulic jack is shown in copending application Ser. No. 737,173, now U.S. Pat. No. 4,144,902; this copending application also being assigned to the assignee of the present invention.